You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
140 lines
5.0 KiB
140 lines
5.0 KiB
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
|
|
|
#ifndef STORAGE_LEVELDB_INCLUDE_DB_H_
|
|
#define STORAGE_LEVELDB_INCLUDE_DB_H_
|
|
|
|
#include <stdint.h>
|
|
#include <stdio.h>
|
|
#include "include/iterator.h"
|
|
#include "include/options.h"
|
|
|
|
namespace leveldb {
|
|
|
|
static const int kMajorVersion = 1;
|
|
static const int kMinorVersion = 0;
|
|
|
|
struct Options;
|
|
struct ReadOptions;
|
|
struct WriteOptions;
|
|
|
|
class Snapshot;
|
|
class WriteBatch;
|
|
|
|
// Some internal types. Clients should ignore.
|
|
class WriteBatchInternal;
|
|
|
|
struct Range {
|
|
Slice start;
|
|
Slice limit;
|
|
|
|
Range(const Slice& s, const Slice& l) : start(s), limit(l) { }
|
|
};
|
|
|
|
// A DB is a persistent ordered map from keys to values.
|
|
class DB {
|
|
public:
|
|
// Open the database with the specified "name".
|
|
// Stores a pointer to a heap-allocated database in *dbptr and returns
|
|
// OK on success.
|
|
// Stores NULL in *dbptr and returns a non-OK status on error.
|
|
// Caller should delete *dbptr when it is no longer needed.
|
|
static Status Open(const Options& options,
|
|
const std::string& name,
|
|
DB** dbptr);
|
|
|
|
DB() { }
|
|
virtual ~DB();
|
|
|
|
// Set the database entry for "key" to "value". Returns OK on success,
|
|
// and a non-OK status on error.
|
|
// Note: consider setting options.sync = false.
|
|
virtual Status Put(const WriteOptions& options,
|
|
const Slice& key,
|
|
const Slice& value) = 0;
|
|
|
|
// Remove the database entry (if any) for "key". Returns OK on
|
|
// success, and a non-OK status on error. It is not an error if "key"
|
|
// did not exist in the database.
|
|
// Note: consider setting options.sync = false.
|
|
virtual Status Delete(const WriteOptions& options, const Slice& key) = 0;
|
|
|
|
// Apply the specified updates to the database.
|
|
// Returns OK on success, non-OK on failure.
|
|
// Note: consider setting options.sync = false.
|
|
virtual Status Write(const WriteOptions& options, WriteBatch* updates) = 0;
|
|
|
|
// If the database contains an entry for "key" store the
|
|
// corresponding value in *value and return OK.
|
|
//
|
|
// If there is no entry for "key" leave *value unchanged and return
|
|
// a status for which Status::IsNotFound() returns true.
|
|
//
|
|
// May return some other Status on an error.
|
|
virtual Status Get(const ReadOptions& options,
|
|
const Slice& key, std::string* value) = 0;
|
|
|
|
// Return a heap-allocated iterator over the contents of the database.
|
|
// The result of NewIterator() is initially invalid (caller must
|
|
// call one of the Seek methods on the iterator before using it).
|
|
//
|
|
// Caller should delete the iterator when it is no longer needed.
|
|
// The returned iterator should be deleted before this db is deleted.
|
|
virtual Iterator* NewIterator(const ReadOptions& options) = 0;
|
|
|
|
// Return a handle to the current DB state. Iterators created with
|
|
// this handle will all observe a stable snapshot of the current DB
|
|
// state. The caller must call ReleaseSnapshot(result) when the
|
|
// snapshot is no longer needed.
|
|
virtual const Snapshot* GetSnapshot() = 0;
|
|
|
|
// Release a previously acquired snapshot. The caller must not
|
|
// use "snapshot" after this call.
|
|
virtual void ReleaseSnapshot(const Snapshot* snapshot) = 0;
|
|
|
|
// DB implementations can export properties about their state
|
|
// via this method. If "property" is a valid property understood by this
|
|
// DB implementation, fills "*value" with its current value and returns
|
|
// true. Otherwise returns false.
|
|
//
|
|
//
|
|
// Valid property names include:
|
|
//
|
|
// "leveldb.num-files-at-level<N>" - return the number of files at level <N>,
|
|
// where <N> is an ASCII representation of a level number (e.g. "0").
|
|
virtual bool GetProperty(const Slice& property, uint64_t* value) = 0;
|
|
|
|
// For each i in [0,n-1], store in "sizes[i]", the approximate
|
|
// file system space used by keys in "[range[i].start .. range[i].limit)".
|
|
//
|
|
// Note that the returned sizes measure file system space usage, so
|
|
// if the user data compresses by a factor of ten, the returned
|
|
// sizes will be one-tenth the size of the corresponding user data size.
|
|
//
|
|
// The results may not include the sizes of recently written data.
|
|
virtual void GetApproximateSizes(const Range* range, int n,
|
|
uint64_t* sizes) = 0;
|
|
|
|
// Possible extensions:
|
|
// (1) Add a method to compact a range of keys
|
|
|
|
private:
|
|
// No copying allowed
|
|
DB(const DB&);
|
|
void operator=(const DB&);
|
|
};
|
|
|
|
// Destroy the contents of the specified database.
|
|
// Be very careful using this method.
|
|
Status DestroyDB(const std::string& name, const Options& options);
|
|
|
|
// If a DB cannot be opened, you may attempt to call this method to
|
|
// resurrect as much of the contents of the database as possible.
|
|
// Some data may be lost, so be careful when calling this function
|
|
// on a database that contains important information.
|
|
Status RepairDB(const std::string& dbname, const Options& options);
|
|
|
|
}
|
|
|
|
#endif // STORAGE_LEVELDB_INCLUDE_DB_H_
|